(1) Field of the Invention
The disclosed invention relates to audio alarm signal devices. More specifically, the disclosed invention provides a device which gradually increases the volume of an audio alarm upon the initiation of the alarm.
(2) Description of the Prior Art
Almost everyone has experienced the startling effect of the initiation of an audio alarm, such as a fire alarm. Indeed, a startling effect is one feature of such alarms in that they are designed to immediately and convincingly warn of a dangerous or even life threatening condition. Audio alarms are also typically high volume alarms so that they can be readily heard above background noise. While these features of audible alarm signals are preferred in the majority of situations when a dangerous condition is to be signaled, there are times when a substantially instantaneous full volume audio alarm initiation is unwanted. For example, an individual who has a heart condition may not: want such a startling alarm initiation sequence for fear of creating undue stress. In addition, when precise operations are being performed, such as explosive material handling or a surgeon performing surgery, a full volume audio alarm signal initiation could have devastating or catastrophic consequences.
Examples of prior art alarm initiation circuits are shown in U.S. Pat. Nos.: 4,523,058; 4,219,799; 4,482,888; 4,237,448; 3,681,916; and 3,931,621. However, none of these prior art patents disclose the precise alarm initiation device taught by the instant application. For example, the '058 Patent (Stevens et al.) is not an automatic alarm device and does not appear to be designed with this feature in mind. Likewise, the '799 Patent (Weber) is not an automatic alarm device and can not produce more than two different sound intensity levels. The '888 Patent (Todaka et al.) does not produce different sound intensities upon alarm initiation but, rather, it varies the frequency of the waveform at the output. In fact, it appears to produce three different frequencies of sound, not four actual intensity levels as is taught by the instant invention. The '448 Patent (Weinberg) teaches a pager with an escalating audio alert signal level. However, this reference does not teach or suggest an alarm initiation device that can be easily reconfigured to vary alarm sound levels between soft and loud levels in any fashion, such as the device disclosed herein, which can be readily changed by simply changing the values of resistors within the device. The '916 Patent (Itoyama et al.) discloses an analog alarm initiation device, not a digital device such as the one disclosed by the instant invention. Accordingly, it suffers from the same limitation described above with respect to Weinberg, namely, it is limited to escalating alarm signals and cannot be reconfigured to allow for any initiation strategy. The '621 Patent (Rose) teaches a device similar to that disclosed in Yatomama et al., namely, an inflexible, analog alarm system.
Accordingly, an audio alarm signal initiation device is needed which could provide a gradual alarm initiation sequence.